Burn rate (chemistry)

About: Burn rate (chemistry) is a research topic. Over the lifetime, 847 publications have been published within this topic receiving 8908 citations. The topic is also known as: Burning rate.

Application of laser-assisted combustion to solid propellant for space propulsion

Abstract: This paper describes laser assisted combustion of solid propellant for small thrusters that can start and interrupt the operation by laser. Burning rates of HTPB/AP composite solid propellants were measured at pressures up to 0.58 MPa with laser power densities up to 0.8 W mm -2 . With some solid propellants, combustion was initiated and interrupted by switching on/off the laser up to 0.58 MPa. Burning rate coincidentally obeyed Vieille’s law with pressure exponents ranging from 0.5 to 0.67. Hence, this suggests that laser assisted combustion is applicable to space propulsion. The heat feedback rate from flame to burning surface, Hf, was estimated from the burning rate variation with laser power density. In case with the fuel-rich solid propellant, Hf ranged from 1.3 to 1.7 W mm -2 . This suggests that approximately 70% of the energy to the burning surface is provided by the combustion itself, and the rest 30 % is supplied by the laser as the supplementary heat flux to compensate for the heat insufficiency for combustion sustenance.

Emulation and Calculation of the Burning Surface of 3D Grains of Partially Cut Multi‐Perforated Stick Propellant using the Level Set Method

Abstract: In order to calculate the burnt mass fraction of complex three-dimensional (3D) propellant grains to meet the requirements of interior ballistic modelling; the level set method is introduced to emulate and calculate the burning surface area of partially cut 7-perforated propellant. The surface evolution and simulation of a 3D grain of partially cut 7-perforated propellant are divided into two parts: the grain configuration initialization and the level set calculation of the propellant regression process. Parallel layer burning is assumed so that the burning surface regresses layer by layer in a direction normal to the surface until the grain is burnt completely. As the burnt mass fraction increases, the remaining propellant volume decreases gradually. The level set method easily simulates the slivering process for complex grain geometries. In this way, the burnt mass fraction of partially cut 7-perforated propellant grain can be calculated by the level set method for the entire combustion process. Results show that the level set method is suitable to capture the burning surface for each burning step and its related parameters, such as the burning area, the remaining propellant volume and burnt mass fraction. More importantly, the level set method gives a possible solution to the coupling of grain combustion with the internal fluid simulation by the pressure and velocity. It is impossible for geometry-based methods to integrate the internal fluid parameters in an interior ballistic model. Also, the level set method will benefit substantially the grain design and lead to improved internal ballistic performance.

Laser-Controlled Combustion of Solid Propellant

Abstract: This paper describes experimental work on laser-controlled combustion of solid propellants. Combustion of AP/HTPB, including ignition, combustion, extinction and re-ignition could be controlled by CO2 laser irradiation at the back pressure of 0.1, 0.3 and 0.5 MPa in nitrogen. Burning rate of propellant increased linearly with the increasing of laser power density. Vieilles law was used here to check pressure effect to burning rate, pressure exponent under different power density (except 0.5 MW/m2) are very close to 0.17.

3D Flow Simulation of Dual Thrust Solid Rocket Motors during Starting Transient

Abstract: Numerical studies have been carried out to examine the pre-ignition chamber dynamics of dual-thrust solid rocket motors. Using a three-dimensional unsteady, second-orderimplicit, shear-stress transport k–ω turbulence model, detailed parametric studies have been carried out to examine conclusively aerodynamic choking and the existence of a fluid throat at the transition region during the startup transient of dual-thrust motors. In the numerical study, a fully implicit finite volume scheme of the compressible, pressure based Navier– Stokes equations is employed. It is confirmed that, at the subsonic inflow conditions, there is a possibility of the occurrence of internal flow choking in dual-thrust motors with large length-to-diameter ratio (L/d > 44) due to the formation of a fluid throat at the beginning of the transition region induced by area blockage caused by boundarylayer-displacement thickness. The internal flow choking results in the formation of shock waves inside the dualthrust motor. The shock waves and the new turbulence level altered the location of the reattachment point and also enhanced the heat flux to the propellant surface, which obviously will lead to undesirable startup transient due to erosive/transient burn rate enhancement. More numerical results of inert simulators of dual-thrust motors with horizontal and flip-horizontal positions are presented with tangible explanations in this paper for establishing the internal flow choking in dual-thrust solid rocket motors with narrow upstream port.